1. Field of the Invention
This invention relates to the field of cellulosic materials, and, in particular, it relates to methods of physically weakening and/or improving the food value of cellulosic materials, to cellulosic compositions useful in such methods, and to compositions containing modified cellulosic materials.
2. Description of the Art
Both urea and sulfuric acid are well known and are widely used in numerous industries for a variety of purposes, including fertilizers, soil adjuvants, chemical treating agents, chemical precursors, and reactants. The ability of sulfuric acid to catalyze a variety of organic reactions is also known. Urea and sulfuric acid are sometimes useful in combination, particularly in the agricultural industry when simultaneous addition of urea and sulfur to the soil is desired.
It is also known that urea and sulfuric acid will combine to form adducts including the monourea-sulfuric acid adduct and the diura-sulfuric acid adduct. For instance, D. F. du Toit, Verslag Akad. Wetenschappen, 22, 573-4 (abstracted in Chemical Abstracts, 8, 2346, 1914) disclosed the phase relationships between the solid phase and saturated solutions containing urea and sulfuric acid at 10.degree. C. and 25.degree. C. The Sulfur Institute, Sulfur Institute Bulletin No. 10 (1964), "Adding Plant Nutrient Sulfur to Fertilizer," disclosed that urea reacts with sulfuric acid to form two complexes of "urea sulfate" which are useful fertilizers. Methods of manufacturing certain combinations of urea and sulfuric acid are disclosed by Verdegaal et al. in U.S. Pat. No. 4,310,343 and by Jones in U.S. Pat. No. 4,116,664.
All animals including warm and cold-blooded animals, such as mammals, fish, birds, and reptiles, can derive at least some food value from cellulosic materials, particularly from cellulosic materials which contain vegetable protein. However, some animals, such as the ruminant mammals, can derive essentially all their food needs from cellulosic materials such as vegetation, notwithstanding the fact that contemporary methods of feeding domesticated ruminant animals usually involve the use of supplements, such as molasses, and other nitrogen sources, such as urea. Thus, while the food value of cellulosic materials can be important to essentially all animals, it is particularly important in the feeding of domesticated ruminant mammals.
Ruminant mammals are members of the suborder Ruminantia comprising even-toed hoofed mammals such as cattle, sheep, deer, camels and the like, which have complex three-or-four-chambered stomachs and the ability to derive nourishment from cellulosic feeds, in part, by virtue of the action of symbiont micro-organisms that assist the animal in breaking down the cellulosic structure. However, it is also known that ruminants have little, if any, ability to break down some more refractory cellulosic feeds such as rice stubble and wood fiber. Efforts to improve the food value of cellulosic materials, including the more refractory cellulosic materials, have been somewhat successful and have usually involved hydrolysis of the cellulosic materials with strong bases such as calcium, potassium and sodium hydroxides at relatively high temperatures, e.g., 300.degree. F., and relatively long contact times. Reaction with lime (calcium hydroxide) is the most commonly studied procedure. However, these procedures are little used, if at all, due to the expense of reactant materials which are consumed during the process, the presence of significant base reaction products, e.g., calcium, potassium, or sodium salts, in the product, and processing costs, all of which make the product uncompetitive economically with known high nutrient value feeds such as alfalfa and grains.
The manufacture of certain commodities from cellulosic materials, such as the manufacture of paper from wood fiber, benefits by the physical weakening and partial breakdown of of the cellulosic structure. Such physical weakening of the cellulosic structure (which results from chemical interaction with one or more reagents) can be accomplished by any one of several methods. One of the most commonly used methods involves treatment with strong base such as calcium, potassium or sodium hydroxides at relatively high temperatures, pressures and contact times. The disposal of cellulosic wastes, such as waste paper, cardboard, wood particles, sawdust, and the like, can also benefit by reducing the bulk and increasing the compressibility of such materials by physically weakening the cellulosic structure of the waste material.
The problems involved in clearing or cultivating land containing significant amounts of brush, undergrowth or crop residue such as rice stubble, wheat stubble, crop vines, etc., after harvest, are very well known to the agricultural and land development industries. Weakening the physical structure of such cellulosic materials would markedly reduce the costs involved in plowing, clearing, harvesting, or otherwise handling such cellulosic materials. In situ treatment with strong base would be difficult if not impossible in most circumstances due to the high temperatures required to obtain realistic reaction rates and to the high cost of reactants that would be involved.
Sulfuric acid is effective for killing live vegetation and, in high enough dosages, will physically weaken the cellulosic structure of vines and other cellulosic materials through oxidation and charring. However, the dosage rates of sulfuric acid required to achieve any significant degree of physical structure weakening are substantial, and thus, they involve considerable expense. Furthermore, the hazards associated with the use of concentrated sulfuric acid are well known, and its application to in situ vegetation at rates required to significantly weaken vines and other vegetation can result in over-acidification of the soil and ecotoxic effects associated with excess acid runoff. Moreover, little, if any, benefit is realized by using concentrated sulfuric acid to modify the physical structure of cellulosic materials or increase the food value of such materials since sulfuric acid chars and destroys the cellulosic structure by oxidation. Thus, sulfuric acid diminishes rather than improves the quality of cellulosic materials to which it is applied.
While crop stubble and undergrowth can be controlled by burning, such practice results in considerable air-borne emissions and has been outlawed in several states. Other states such as Oregon that still allow burning charge for burning permits which make that alternative economically unattractive.
Obviously, waste cellulose can be disposed of as refuse or incinerated, while in situ vegetation, such as crop stubble, can be cleared or plowed under by mechanical means. However, the energy costs, time, and capital investment involved in such procedures are relatively high, and they often do not reclaim any potential value of the cellulosic material involved.
Accordingly, a need exists for improved methods of modifying cellulosic materials, for compositions useful in effecting the modifications of cellulosic materials, and for improved, modified, cellulosic compositions. In particular, a need exists for improved methods for (1) of physically weakening cellulosic materials, (2) chemically modifying cellulosic materials, and/or (3) improving the food value of cellulosic materials.
It is therefore one object of this invention to provide methods for modifying cellulosic materials.
It is another object to provide methods for weakening the physical structure of cellulosic materials without charring the cellulose content thereof.
Another object is the provision of modified cellulosic materials.
Another object is the provision of cellulosic materials having weakened physical structure and reduced resistance to deformation and shear.
Another object is the provision of improved methods for reducing the physical strength of in situ crop residues such as crop stubble.
Another object is the provision of improved methods for clearing agricultural fields and/or fields containing indigenous vegetation.
Another object is the provision of methods for improving the food value of cellulosic materials.
Another object of this invention is the provision of methods for improving the food value of ruminant fees.
Yet another object of this invention is the provision of novel compositions useful in the production of modified cellulosic materials.
Other objects, aspects and advantages of this invention will be apparent to one skilled in the art in view of the following disclosure, the drawing and the appended claims.